pre-vāil'ing, predominant, gen wān'ing, decreasing towards (5) St. Peter's: i.e., St. Peter's Cathedral at Rome, the largest Christian church-building in the world. The dome, designed about 1546 by the famous sculptor Michael Angelo, has a diameter of nearly two hundred feet. (5) St. Paul's: i.e., St. Paul's Cathedral in London, next to St. Peter's the largest of Christian edifices, was designed by the famous architect Sir Christopher Wren, and was finished in 1710. Its dome is one hundred and forty-five feet in diameter. 1. It is one of the privileges of man to have eyes. Many living creatures have none. The eyes, for example, which the starfishes have, are mere sensitive points dimly conscious of light and darkness, but not perceiving colors or distinguishing forms. The eyes of flies are hard horny lanterns which can not be moved about like our restless eyes, but look always in the same direction; whilst spiders, having many more things to look after than one pair of such lanterns will suffice for, have eyes stuck all over their heads, and can watch a gnat with one eye, and peer through a hole in their webs with another. 2. We are much better provided for than any of these creatures, although we have but two small orbs to see with. Think how beautiful the human eye is, excelling in beauty the eye of any other creature. 3. Yet the eyes of many of the lower animals are very beautiful. You must have admired the bold, fierce, bright eye of the eagle; the large, gentle, brown eye of the ox; the green eye of the cat, waxing and waning like the moon, as the sun shines upon it or deserts it; the pert eye of the sparrow; the sly eye of the fox; the peering little bead of black enamel in the mouse's head; the gem-like eye which redeems the toad from ugliness; and the intelligent, affectionate expression which looks out from the human-like eye of the horse and the dog. 4. There are these and the eyes of many other animals full of beauty; there are none, indeed, which are not beautiful: but there is a glory, which excelleth in the eye of man. We see this fully only when we gaze into the faces of those we love. It is their eyes we look at when we are near them, and recall when we are far away. The face is a blank without the eye. 5. But apart altogether from its beauty, the human eye is a wondrous construction. Let us glance for a moment at it. It is a hollow globe, or small round chamber. There is no human chamber like it in form, unless we include among human dwelling places the great hollow balls which surmount the domes of St. Peter's and St. Paul's. The eye is such a ball. 6. The larger part of it, which we do not see, forms the white of the eye, and consists of a strong, thick, tough membrane, something like parchment, but more pliable. This forms the outer wall, as it were, of the chamber of the eye; it may be compared to the cup of an acorn, or to a still more familiar thing, an eggcup, or to a round wineglass with a narrow stem. It is strong, so that it can not easily be injured; thick, so that light can not pass through it; and round, so that it can be moved about in every direction, and let us see much better on all sides with a single pair of eyes than the spider can with its host of them. 7. In the front of the eye is a clear, transparent window, much like the glass of a watch. If you look at a face sideways, you see it projecting with a bent surface like a bow window. The eyelids may be compared to a pair of outside shutters for this window, which are put up when we go to sleep, and taken down when we awake. But these shutters are not useless. Every waking moment they are rising and falling, or, as we say, winking. We do this so often that we forget that we do it at all; but the object of this winking is a very important one. 8. An outside window soon gets soiled and dirty, and a careful shopkeeper cleans his windows every morning. But our eye windows must never have so much as a speck or spot upon them; and the winking eyelid is the busy apprentice who, not once a day, but all the day, keeps the living glass clean: so that after all we are little worse off than the fishes, who bathe their eyes every moment. 9. Behind this ever clean window, and at some distance from it, hangs that beautiful circular curtain which forms the colored part of the eye, and in the center of which is the pupil. It is named the iris, which is only another name for rainbow; for though we speak of eyes as simply blue, or gray, or black, because they have one prevailing tint, we can not fail to notice that the ring of the eye is always mottled, and flecked or streaked with colors as the rainbow is. 10. This rainbow curtain, or iris, answers the same purpose that a Venetian blind does. Like it, it can be opened and closed at intervals, and it is never closed altogether; but it is a far more wonderful piece of work than a Venetian blind, and it opens and closes in a different way. The iris opens widest in utter darkness, and closes so as to make the pupil a mere black point when sunshine falls upon it. 11. If we wish to observe this in our own eyes, we need only close them for a little while before a lookingglass, so that the dropped eyelids may shut out the day, when, like shy night birds, the living circles will stretch outwards; and the pupil of the eye, like a hole which the sun is melting in the ice, will quickly widen into a deep, clear pool. If now we open our eyes, we see the rainbow rings contract as the light falls upon them, and the dark pupil rapidly narrow. 12. But probably all have seen the movement I am describing in the eyes of a cat, where the change is more visible than in our own eyes; and have noticed the broad iris spread out in twilight, till the look is softened into a mild glance; whilst when pussy is basking in the sun, as she dearly loves to do, she shows between her frequent winkings only a narrow slit for a pupil, like the chink of a shutter. 13. The endless motions of this living curtain, which, like the restless sea, is ever changing its aspect, have for their object the regulation of the flow of light into the eye. When the permitted number of rays have passed through the guarded entrance or pupil, they traverse certain crystal-like structures, which are now to be described. 14. Behind the iris is a lens or magnifying glass. We are most familiar with this portion of the eye as it occurs in fishes, looking in the recently-caught creature like a small ball of glass, and changing into what resembles a ball of chalk when the fish is boiled. This lens is enclosed in a transparent covering, which is so united at its edges to the walls of the eye, that it stretches like a piece of crystal between them; and in front of it, filling the space dividing the lens from the watchglass-like window, is a clear transparent liquid like water, in which the iris floats. 15. The lens is set like the jewel stone of a ring, in what looks like a larger sphere of crystal, but which in reality is a clear liquid contained in an equally clear membrane: so that the greater part of the eye is |